Cron import users in joomla

The client has a joomla website, already with some users in it. He uses an external software to manage his members, now he wants to import those members into a joomla site to provide them login and access to the memberpart of the site. You need to write the automatic import script (CSV is delivered by client) and it should be activeted by CRON. CSV contains : language, title, name, firstname, login, password, email, ID & Group. (see attach) After import, a mail should be sent to the members who are new in the csv file, old members should not receive a mail. the ID is also used as joomla ID. The client must also be able to manually add users in joomla without making this a problem for the import (ID!!!)